The present invention relates generally to the metal casting field wherein molten steel may be continuously cast into a slab of steel, and more particularly to an apparatus for introducing a granular mold flux onto the top of the slab being cast within a continuous casting mold.
It is customary to apply a mold flux, which may be a powder or granular material, onto the top of a slab during continuous casting of a molten metal, typically steel, as shown in U.S. Pat. No. 4,084,626, the flux turning into slag when sufficiently heated by the molten steel. In practice, it is desirable to have about 1-3 inches of flux or slag on top of the mold during casting. The device illustrated in the foregoing patent is for feeding a mold flux in the form of a powder. The powder has poor flow characteristics, and thus a screw feed mechanism is used, which screw extends between an intermediate hopper (or bin) and the top of the slab being cast. This form of device is somewhat expensive and, in fact, is not typically used in industry because of its cost and unreliable operation. Thus, it is common today to merely sweep the mold flux onto the top of the slab when desired, the flux being provided in 10 kg. bags. This system works well, but it is manpower intensive. In addition, it is environmentally unfriendly as there is a lot of refuse from the empty 10 kg. bags.
U.S. Pat. Nos. 4,595,045 and 5,158,129 disclose method and apparatus for applying a layer of flux to the top of a slab being cast. In both of these designs, the delivery pipe (or supply pipe) is positioned slightly above the predetermined powder height, so that flow through the pipe is regulated by how fast the flux material flows away from the discharge end of the pipe. Thus, when the powder level drops below the delivery end opening, material flows from the pipe. This form of apparatus, which relies solely upon the flow of material away from the delivery pipe, has not always been satisfactory since occasionally the end of the delivery pipe will become blocked by slag or the like, and rigid piping at a sufficient flow angle is needed that is too much of a hindrance at the caster.
It is an object of the present invention to provide an apparatus for introducing a granular mold flux onto the top of a slab being cast within a continuous casting mold wherein the flux may be introduced at a substantially constant rate.
It is a further object of the present invention to provide an apparatus for introducing a granular mold flux onto the top of a slab being cast within a continuous casting mold which is environmentally friendly, of low cost, and reliable.
It is yet another object of the present invention to provide an apparatus of the type set forth above which requires less manpower and permits remote operator control unlike commonly used systems of today.
More particularly, it is an object of this invention to provide an apparatus having delivery means for feeding granular mold flux from an intermediate hopper to the top of the slab being cast, the delivery means including at least one delivery tube assembly interconnected with the intermediate hopper, and a variable pinch valve located between the intermediate hopper and the delivery tube for controlling the flow rate of the granular mold flux through the delivery tube.
It is a further object of the present invention to provide, in an apparatus of the type set forth above, a source of granular mold flux and transfer means for transferring the granular mold flux from the source of the granular mold flux to an intermediate hopper, the intermediate hopper being provided with a sensor for controlling the level of granular mold flux within the intermediate hopper.
In summary, the foregoing objects are accomplished by providing an apparatus consisting of a vacuum transfer system which transfers the granular mold flux from a source of granular mold flux, which may be a large bulk bag (approximately 4-5 ft. on each side) to an intermediate hopper provided with a sensor a suitable distance above the bottom of the intermediate hopper. The intermediate hopper is capable of being mounted on a side of a tundish. If the sensor is covered with flux, the vacuum transfer system will be turned xe2x80x9coffxe2x80x9d; but when the sensor is uncovered, the transfer system will be turned xe2x80x9conxe2x80x9d to refill the intermediate hopper until the sensor is again covered. From the intermediate hopper, the flux will flow through at least one delivery tube assembly onto the top of the slab being cast, which delivery tube assembly includes a delivery tube. In one embodiment the flux flows through the delivery tube assembly by gravity. In another embodiment the flow of flux through the delivery tube assembly is assured by an inline air pump. It is a feature of this invention to control the flow rate of the flux being delivered, so that the delivery rate is equal to that rate of the flux which is being consumed during casting, this being done by at least one pneumatically operated pinch valve. Thus, a pinch valve is located at the input side of each delivery tube. The diameter of the pinch valve is controlled by an operator via a control device, and in operation, the operator will set the control for the desired flow rate. If it is not right, as will be determined via a visual inspection of the top of the slab, it will be adjusted.
It is a further object of the present invention to provide an apparatus which utilizes air pumps to transfer a granular mold flux onto the top of a slab being cast within a continuous casting mold, the apparatus including a source of granular mold flux, an intermediate hopper, and one or more delivery tube assemblies interconnected with the intermediate hopper, each delivery tube assembly including an inline air pump and a flexible line, the inline air pump assuring a positive flow of flux through the flexible line. In one variation the flow rate of flux is controlled by a pinch valve, while in other variations the flow rate is controlled by varying the air volume delivered to the air pump.
The foregoing objects and other objects and advantages of this invention will become more apparent after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of this invention is illustrated.